1. Field of the Invention
The present invention concerns the manufacture of pivots having a hollow, spherical head, or ball, of the type used in the suspension or steering joints in the automobile industry made by cold forging.
2. Description of the Prior Art
In manufacturing processes such as This, the spherical head is casually formed by an initial reverse threading, giving the end of the pivot an almost hemispherical base of attachment to its rod, extended toward the extremity by a threaded, tubular part. This form is then placed between two hemispherical dies, which push the outer edge of the tubular part inwards, resulting in an almost spherical outer form and an inner cavity, also practically spherical, open on its extremity.
The advantage of this hollow shape, in addition to a savings in metal, which can be considerable in mass production, lies in the lesser amount of energy needed for forming the hollow, spherical head, compared with the forming of a solid ball-joint. The lighter parts are also advantageous, particularly for the suspension elements connected to the wheels, which therefore are unsuspended, and must be as light as possible.
Very narrow manufacturing tolerances are required for the dimensions of the heads and have, up until now, necessitated machining after the forging operation.